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Author Topic: Active power from parallel resonance. Test circuit and research.  (Read 14904 times)

Jim36

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Active power from parallel resonance. Test circuit and research.
« on: February 16, 2016, 11:56:33 PM »
Hi all,

I have a new idea and would like people to have a look at as it is quite simple. I have seen some experienced electronic guys on here so hope to get some feed back before building.

See attached circuit diagram. From my calcs the capacitor & inductor can store just over 1 joules per cycle. The current circuit would only use 50 % of the cycles but another circuit could be added to use the full wave cycle.

The circuit should work by triac T1 firing on the first half cycle which should start the resonance circuit. In theory the parallel LC circuit shouldn't draw any current from outside its own circuit. During the second cycle T1 stops conducting decoupling from the mains and T2 should fire on the negative cycle produced by the LC tank and power dissipated through the dampening load. The cycle then starts again.

Thanks for looking, and I welcome any comments.

Cheers

Jim
« Last Edit: February 23, 2016, 02:22:51 AM by gotoluc »

pomodoro

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #1 on: February 17, 2016, 12:46:37 AM »
Is this for OU or for some other purpose?


Cheers, Pomo  8)

citfta

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #2 on: February 17, 2016, 12:51:26 AM »
If you want some help you need to reduce the size of your drawing to the size recommended for this forum.  Otherwise no one can see all of it without scrolling back and forth.  You can edit your post and remove the attachment and then insert a smaller drawing the does not go way beyond the normal width of the forum.  There are several free picture editing programs on the net you can get if you need one to help you reduce the size.  I use one called "Free Photo Converter".  Very easy to use and works great.

verpies

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #3 on: February 17, 2016, 01:33:29 AM »
See attached circuit diagram. From my calcs the capacitor & inductor can store just over 1 joules per cycle.
1 Joule is a lot in electronics.
But why do you think that the parallel LC circuit will give up more energy then it took to energize it?

During the second cycle T1 stops conducting decoupling from the mains and T2 should fire on the negative cycle produced by the LC tank and power dissipated through the dampening load. The cycle then starts again.
Please compare the forward voltage drop of a Triac vs. a MOSFET, while keeping in mind that the power lost inside the Triac is equal to the product of the current flowing through it and its voltage drop.

sm0ky2

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #4 on: February 17, 2016, 01:37:28 AM »
here

Jim36

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #5 on: February 17, 2016, 11:35:06 AM »
Pomo, yes it's a circuit for OU (I hope). :)

Verpies,
1 Joule is a lot in electronics.
But why do you think that the parallel LC circuit will give up more energy then it took to energize it?
Please compare the forward voltage drop of a Triac vs. a MOSFET, while keeping in mind that the power lost inside the Triac is equal to the product of the current flowing through it and its voltage drop.


Yes I know 1 joule is a large amount for electronics, this is a power device utilising mains rated power electronics to switch on and off close to 0V on each half cycle. Actually I calculate it at 1.44Joule though there will be parasitic losses not accounted for like you said across the Triac (I will calculate this). And also losses within the inductor / capacitor parallel circuit though I will size the wire to be able to handle large current and the inductor will be from a transformer primary, capacitor will be a motor run type.

This is what I want to run by you. Why does a parallel LC circuit (tuned to resonance) draw any current on start up when an AC voltage is applied? I haven't practically tested it and probably missing something as it does seem too simple. My thoughts are the capacitor and inductor will require equal current at the same time but of opposite direction as they are 180 degrees out of phase, therefore the current cycles between them selves and does not draw from the mains?

SmOky2, thanks for editing the picture :)

Cheers



sm0ky2

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #6 on: February 17, 2016, 11:50:27 AM »

SmOky2, thanks for editing the picture :)

Cheers

no problem.  If you go back and edit your original post, removing the (large) photo, it will resize the thread page and make it easier for people to view.


the problem I see here, is going to be a difference in Impedance between the tank circuit and the other parts of the circuit.
namely T2, and the common lead back to source.

sm0ky2

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #7 on: February 17, 2016, 11:53:56 AM »
this creates a reactance, to the source.
which will alter the measurement of power input if not properly accounted for.

verpies

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #8 on: February 17, 2016, 01:33:15 PM »
Why does a parallel LC circuit (tuned to resonance) draw any current on start up when an AC voltage is applied?
Because the phase offset between the external AC voltage and the internal AC voltage across the parallel LC circuit is not 0º.
This phase offset occurs not only during startup but also any time that phase of the external AC voltage is changed.

Most importantly, the current draw happens anytime the voltage across the capacitor is smaller than the instantaneous voltage of the the external AC voltage.

Jim36

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #9 on: February 17, 2016, 03:46:00 PM »
Smoky2, I can't edit the original post only my later replies for some reason? I'm new to the forum so having a few teething issues! If you could point me in the right direction :)

Verpies, Thanks for your explanation. You say that a phase offset between the source voltage and voltage across the circuit
cause an initial current draw to charge the parallel circuit which would be exactly the same amount of current as a capacitor only circuit
or inductor only circuit? What phase angle is this initial current with the source voltage? Have you seen this under test
circumstance yourself? I can't find any information on this phenomenon so would appreciate any links to help explain.

Thanks

verpies

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #10 on: February 17, 2016, 05:01:02 PM »
You say that a phase offset between the source voltage and voltage across the circuit cause an initial current draw to charge the parallel circuit
Yes

which would be exactly the same amount of current as a capacitor only circuit or inductor only circuit?
No.
The initial current drawn by a single capacitor (or single inductor) would be less than both.

What phase angle is this initial current with the source voltage?
180º

Have you seen this under test circumstance yourself?
Yes

I can't find any information on this phenomenon so would appreciate any links to help explain.
For example this link.

You can click on the SPST switch to close it. You can double click on any component to edit it.
The green scope trace represents voltage and the yellow trace represents current.
Hovering over a scope trace highlights in blue the component that the trace refers to.

FatBird

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #11 on: February 17, 2016, 05:28:28 PM »
Where are the Output Terminals?


                                                                                          .

verpies

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #12 on: February 17, 2016, 07:08:32 PM »
Where are the Output Terminals?                                                                                    .
To which circuit are you referring to?

Jim36

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #13 on: February 17, 2016, 08:16:05 PM »
Hi Verpies, the only problem with the simulation is the series resistor as I was looking at 0.3 ohms due to wiring only, the dampening resistor would be in parallel and switched in on the
second half of a cycle.
Have you actually seen this happen in a physical circuit? I suppose in electronics this is something you might come across often enough. If so I think this thread has been answered and
you have saved me some time!!
Thanks for all the information you have given me.

Cheers

Jim

Jim36

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Re: Active power from parallel resonance. Test circuit and research.
« Reply #14 on: February 17, 2016, 09:23:22 PM »
Where are the Output Terminals?


                                                                                          .

The output terminals would be across the load as that is where I was looking to dissipate power.